Heat extraction system for a high temperature heat source



Oct. 22, 1963 D. ARONSON 3,107,655

HEAT EXTRACTION SYSTEM FOR A HIGH TEMPERATURE HEAT SOURCE Filed Nov. 8, 1960 2 Sheets-Sheet 1 22 |8 SoDluM SODIUM F i 2z l D000 F l |200 i |l '3, |7 I6 '9 |9\ 7N `.I l 4 L L -z/b z2 H |4- 04? i9 TEMPERATURE CONTROL- 47 49 To TuRemE ",eooLs/na.

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Oct. 22, 1963 D. ARoNsoN 3,107,655

HEAT EXTRACTION SYSTEM FOR A HIGH TEMPERATURE HEAT SOURCE Filed Nov. e, 19Go Y 2 sheets-sheet 2 TO TURBINE BolLE (ze HEAT TO BOILER DAV! D ARONSON IN VEN TOR.

3,107,655 HEAT EXTRACTHGN SYSTEM FR A HGH TER/PERATURE HEA SURCE David Aronson, Upper Montclair, NJ., assigner to Worthington Corporation, Harrison, NJ., a corporau tion of Delaware Filed Nov. 8, 19%0, Ser. No. :58,6% Claims. (Cl. 122-32) This invention relates to heat extraction from a high temperatur-e heat source under conditions of high heat ux. It includes a steam circuit with a multi-pass superheater for heat exchange with a heat source material.

Instances arise wherein change of phase of the heat receiving fluid during heat transfer is undesirable because of the pulsating and transient nature of the phenomenon. One adverse elect of varying conditions is the non-uniform change of temperature, producing stresses which give rise to leakage.

One solution to the change of phase problem is to transfer the heat to highly pressurized water without change of phase. However, this approach limits the ternperature of water leaving the system to a value in the range of the critical temperature.

Another approach to avoid the change of phase problem has been to use an inert gas such as helium or nitrogen in lan intermediate cycle between the heat source and the power plant steam cycle. This approach requires blowers to circulate the inert gas which complicates the system.

The present advance covers a heat extraction system wherein a relatively small superheater vessel has a high temperature heat source material disposed therein and is provided with a plurality of series connected steam flow paths for passing steam in successive passes in superheat relationship with the high temperature material. Addition means connected intermediate of the superheater passes desuperheat the steam and add to the steam quantity so that the input steam requirement may be small. The required quantity of steam at a suitable temperature and pressure is attainable by multiple passes through the vessel. One `of the desuperheat stages is of the indirect contact type provided by passing the superheated steam through the boiler to produce the initial input steam.

This combination provides numerous advantages. It is a simple and compact system. Safety is enhanced by the elimination of thermal stresses because there is no water phase change in the superheater vessel. Multiple passes of the steam through the superheater vessel Wtih lower pressure in each subsequent pass eliminates the need for blowers. Superheated steam may be used to produce the steam in the boiler so that after start up steam production is completely sustainable by a desuperheat pass of superheated steam through the boiler. Communicating the addition means with the boiler feed pump simpliies the circulation. Blending of superheated and desuperheated steam is available as a means for controlling turbine input characteristics.

In nuclear applications this advance offers additional advantages. Free hydrogen and oxygen aggravate corrosion in the steam cycle. In this regard, decomposition of water molecules progresses as a function of how long Water is exposed to radiation. This heat yextraction sy" tern substantially reduces residence time from that in a comparable boiling water system because of lower steam density and also because of the small size requirement for the superheater vessel.

Water leakage into a high temperature material such as liquid metal is highly undesirable. By the present ad- Vance, the superheater vessel contains only steam. In the event of a steam to liquid metal leak, as compared Patented ct. 9.5.2, 19%3 Lfd to a water to liquid metal leak, a lesser mass of water would be introduced into the liquid metal system. Accordingly, a much longer time would be available for action to correct the situation.

These and other advantages will be seen more fully from the speciication including claims viewed in conjunction with the accompanying drawing of a heat cxtraction system embodying the present invention wherein:

FIGURE 1 is a fragmentary view of the superheater vessel according to the present invention.

FIGURE 2 is a schematic diagram of the heat extraction system with design ilows for a portable reactor superimposed thereon. The ends of the superheater vessel are represented in mirrored relationship'.

FIGURE 3 is a temperature-entropy representation of the heat extraction system.

FIGURE 4 is an enlarged representation of the addition means to desuperheat the steam and add to the steam quantity intermediate of the superheater passes.

This heat extraction system is applicable to any system wherein steam is used Without phase change in heat exchange with a high temperature heat source. The specic embodiment of the invention shown in the drawings pertains to a liquid metal cooled nuclear power plant.

As is shown in FIGURE 1, liquid metal, here sodium, is used as a high temperature primary liquid heat transfer medium which is circulated through the region of nuclear heat generation (not shown). Where heat iluxes permit, it is entirely possible to circulate the steam directly through the reactor.

Any substance suitable for use in heat exchange with a nuclear heat source could serve as the primary liquid. The sodium circulates through a radiation shielded closed circuit shown in yFIGURE l which includes in series both the region of nuclear heat generation and the superheater vessel generally described l1. Liquid sodium which permits lthe attainment of high heat ilux because of its high heat transfer is `especially suited to portable applications. Radiation shielding such as lead (not shown) is required because the liquid metal becomes radioactive in this service.

Using a multi-pass superheater with intermediate desuperheating and Working uid addition permits a high degree of heat extraction from the hot liquid sodium. Superheater vessel 11 includes elongated shell l2, tubes i3 and a pair of header plates 14 and is generally fabricated in all-welded construction. Liquid sodium enters superheater vessel ll through girth belt 16 which provides a uniform heat distribution. Shield 17 protects tubes i3 from the incoming liquid metal. The sodium courses past the outsides `of tubes 13 through vessel lll and exits via girth belt 18. By the shown tube and shell arrange ment the interior of the tubes are disposed in non-contacting heat exchange relationship with liquid sodium. Radial partitions 19 divide the ends of vessel ll outside of header plates l@ into paired chambers which divide tubes 13 into sector groups. Radial partitions i9 are connected between header plates 1d and shell l2. Flow through all sector groups of tubes is arranged opposite to the general direction of iioW of the liquid sodium. Superheat paths as shown include a sector group of tubes and the pair of end chambers communicating therewith. The number, form and fabrication of the superheat paths improve with developments in tube and shell welding techniques. In the shown embodiment the first superheat path is designated l and the last superheat path is designated 9. A plurality of ports are formed in the shell so that each port communicates with one -of the end chambers, thus, the ports define the upstream end 22 and the downstream end 23 of each superheater path.

Conduit means, shown in FIGURE 2 as conduits, two

less in number than the number of superheat paths, are connected with each conduit communicatingthe downstream end 23 of one path with the upstream end 22 of the next so that said paths form successive superheater passes. The circulating of superheated steam through boiler 26 provides the last desuperheat. in this manner conduits 24 are interposed in flow series alternately with the superheat paths.'

Steam is passed through the successive superheater passes to extract heat from the liquid sodium for use with turbines or Vother prime movers.

The steam is generated in vaporizing means shown as boiler 26 receiving water from any convenient source which would usually be a condenser of a steam cycle (not shown). In the shown embodiment the boiler is heated by non-contacting heat exchange with the superheated steam. Feed means shown to include in series boiler feed pump 27 communicate the source of water with boiler 26. Delivery means 2S Communicate boiler 26 with the upstream port 29 of first superheat path l to deliver steam thereto for superheating.

Intermediate of superheater passes the steam must be conditioned for succeeding passes. After leaving the downstream port 31 of first superheat path 1 the superheated steam enters conduit means shown as conduit 32 which communicates downstream port 31 of rst superheat path l and upstream port 33 of second path 2. Addition means 34 communicate the source of water (not shown) with conduit 32 to add water to lthe conduit 32 desuperheating the steam and adding to the quantity of steam in advance of succeeding superheater passes. Nozzle means are disposed in the conduit means whereby water `from the source is sprayed downstream into the conduit. Addition means 34 communicate the source of water and conduit `32 -via boiler lfeed pump 27 thereby avoiding the necessity of auxiliary pumping equipment. After passing through second superheat path 2 the steam is communicated to conduit 36 where the next charge of Water is -added `at 37 in advance of third superheat path 3. As in conduits 32 and 36 each succeeding spray charge of water in conduits 38, 39, 41, 42 and 43 desuperheats the steam by taking heat therefrom and adds to the steam quantity. -In this manner -a temperature gradient for heat exchange ywith the succeeding superheater pass -is developed. As in the spray charge desuperheater process conducted in conduits 32 and 36, thespray charge of water in succeeding conduits is also vaporized so that only steam enters the superheater thereby eliminating change of phase thermalstresses. The successive supe-rheat paths 3, 4, 5, 6, 7 4and 8 and intermediate desupe heat conduits 38, 39, di, y42 and `43 tare likewise traversed until the next to last superheat path 8 (in the shown embodiment the eighth superheat path) has been completed. vThe steam is then conducted by means'of pipe to boiler 26 where it provides the heat necessary to produce input steam for first superheat path 1. In producing steam -from the superheated steam is desup'erheated in advance of the last superheat path 9. Pipe 46 delivers the desuperheated steam from boiler 26 to last superheat path 9. The superheated steam passes out downstream port 47 of las-t superheat path 9 to removal means shown as pipe 4S :for communication to a turbine or other suitable prime mover (not shown). These relationships are shown in the temperature-entropy representation of FIGURE 3 with corresponding flow locations indicated thereon.

Versatile turbine input characteristics are obtainable b y the blending of superheated and desuperheated steam. To accomplish this blending, pipe '49 communicates pipe i6 with removal means 47 so that desuperheated steam from upstream of last superheat path 9 can be delivered to rernoval means 47. As `an alternative -to pipe 49, any suitable source of desuperheated steam could be employed. Turbine input characteristics could also be controlled by i attemperation spraying downstream of removal means or other known techniques.

Water is communicated from downstream of boiler feed pump 27 by conduit 53 (not fully shown) to addition neans lwhich appears in greater detail in FIGURE A.. Enlarged portion S4 has nozzle means 56 mounted therein and directed downstream relative conduit 32. Not all of the water added by nozzle 56 evaporates. The liquid phase collects in recess 57. Orifice 5S defined by plate 59 meters the flow of water to addition means 37 of conduit 36 so that water level `61 is maintained in recess S7 thereby inhibiting the shortV circuiting of steam from conduit 32 to .conduit 36 and providing a surface upon which the pressure difference between conduit 32 and conduit 36 can act to inject water into addition Ameans 37. In similar fashion water is added to conduits 3S, 39, 41, 42 and 43. The excess water is conducted via conduit 62 to the deacrator of the steam cycle or some other suitable location upstream of boiler feed pump 27.

Design estimates representative for a steam cycle heat extraction system of a portable nuclear generator set `are superimposed on the drawing. These figures show the Iaddition of water atcondu-its 32, 36, 38, 39, 41, 42 and 43 `and the building up of steam quantity from 2,620 lb./hour to 11,900' lb./hour. The boiler capacity required is only 2,620 lb./hou-r. Boiler 26 with associated feed Water heater 51 and steam drum 452 are of known design but are characterized by their small size occasioned -by the requirement of only 2,62() lb./hour steam output required for first superheat path 1. `In the design shown a 26 U-tube, 3i OD., V15G() p.s.i.a., 6 diameter pipe shell boiler is called for. As the number of superheater passes is increased the boiler size can be further reduced. Of

v course the quantities here set forth are only significant for this example.

The system may be started by filling the superheat paths with water and Vgradually building up the heat of the heat source material or an auxiliary steam source may be used.

Turbine operation is a representative application of this heat extraction system. Further, within the context of this specification it will be understood lby those skilled in thermodynami'cs that iwide changes may be ymade in the details of construction and the correlation of the various elements of this heat extraction system Without departing,r from the scope of the `invention yas deined by the claims.

What is claimed is:

l. In a compact heat extraction system having a single phase gas pass in heat exchange relation with a high temperature heat source means (a) a rvessel having said heat source means pass therethrough,

(b) said vessel having a plurality of superheat paths Vtherethrough in non-contacting heat exchange relationship rwith saidy heat source means,

(c) a plurality of conduit means communicating said superheat paths in a single flow series whereby said paths deine a rst path, intermediate path and a last path,

Y (d) the iirst of said conduit means connected to a source of steam and said steam adapted to be successively passed `through said paths for superheating thereof,

(e) addition means communicating with each of said conduit means, except the one connected to the last path, to add water to said conduit means intermediate of each successive path to desuperheat said superheated steam and to increase the `quantity thereof,

(f) removal means connected to said l-ast path for removing superheated steaim from Ysaid vessel.

2. In 'a compact heat extraction system having a single phase gas pass in heat exchange relation with a nuclear Vheat source having a radiation shielded closed circuit with a primary liquid circulating through a region of nuclear heat generation (a) said heat extraction system comprising a vessel through which said prima-ry liquid circulates,

(b) said vessel having a plurality of superheat paths therethrough disposed in non-contacting heat exchange relationship With said primary liquid,

(c) a plurality of conduit means disposed outside said vessel to connect said paths in a single ow series so that said paths define successive superheater passes,

(d) delivery means communicating With a steam source and to deliver steam to the iirst of said paths,

(e) laddition means communicating with said conduit means to add -Water to said conduit means intenmediate of said successive superheater passes to desuperheat the superheated steam and to be vaporized by said superheated steam to increase the quantity thereof,

(f) means connected to the last of said paths and adapted to remove superheated steam therefrom.

3. In a compact heat extraction system having a single phase gas pass in heat exchange relation with a nuclear heat source having a radiation shielded closed circuit with liquid metal -circulating through a region of nuclear heat :generation (a) a vessel through which said liquid metal circulates and including a shell, tubes and header plates connected in said shell and defining a tube arrangement therethrough disposed in non-contacting heat exchange relationship with said liquid metal which circulates through said vessel,

(b) partition means at each end of said vessel and connected to said header plates and to said `shell to group said tubes into sector groups to deline a plurality of superheat paths through said vessel,

(c) a plurality of ports formed in said shell at each end,

(d) one of said ports communicating `with each of said sector groups at each end thereof so that said ports deine respectively the upstream and downstream ports of said paths,

(e) a plurality of conduit means interposed in ow series with said paths IWith each conduit communicating the downstream port of one path with the upstream port of the next path so that said paths form successive superheater passes and said passes define la iirst path, intermediate paths and a last path,

(f) delivery means connected to a source of steam and communicating with said first path to deliver steam thereto,

(g) addition means communicating with said conduit lmeans to add Water to -said `conduit means cooling superheated steam in ladvance of succeeding superhea-ter passes and to increase the steam ow in each of the succeeding superheater passes,

(h) said successive superheater passes increasing in ilow capacity to accommodate a progressively increasing steam flow,

(i) removal means communicating with the downstream port of said last path for removing superheated steam.

4. The combination claimed in claim 1 wherein (a) said paths extend substantially the full length of said vessel,

(b) said heat source means pass in heat exchange reylation with the steam in said paths through less than the full length of said vessel.

5. The combination claimed in claim 1 wherein bypass means connected between said conduit means before lthe last path and said removal means and adapted to communicate a portion of the -desuperheated steam :from the next to -last path with the superheated steam from the last path `whereby the desired steam characteristics can be obtained.

References Cited in the le of this patent UNITED STATES PATENTS 455,471 Caven July 7, 1891 2,957,815 Pecault et al Oct. 25, 1960 2,975,118 Tognoni Mar. 14, 19'61 i2,982,263 Villiers et al. May 2, 1961 FOREIGN PATENTS 335,080 Great Britain Sept. 18, 1930 1,218,206 France Dec. y14, 1959 OTHER REFERENCES Chemical Engineers Hand-book, 3rd. ed., pp. 1215-1217. Principles of Nuclear Reactor Engineering, page 524, topic 8.247. v 

1. IN A COMPACT HEAT EXTRACTION SYSTEM HAVING A SINGLE PHASE GAS PASS IN HEAT EXCHANGE RELATION WITH A HIGH TEMPERATURE HEAT SOURCE MEANS (A) A VESSEL HAVING SAID HEAT SOURCE MEANS GAS THERETHROUGH, (B) SAID VESSEL HAVING A PLURALITY OF SUPERHEAT PATHS THERETHROUGH IN NON-CONTACTING HEAT EXCHANGE RELATIONSHIP WITH SAID HEAT SOURCE MEANS, (C) A PLURALITY OF CONDUIT MEANS COMMUNICATING SAID SUPERHEAT PATHS IN A SINGLE FLOW SERIES WHEREBY SAID PATHS DEFINE A FIRST PATH, INTERMEDIATE PATH AND A LAST PATH, (D) THE FIRST OF SAID CONDUIT MEANS CONNECTED TO A SOURCE OF STEAM AND SAID STEAM ADAPTED TO BE SUCCESSIVELY PASSED THROUGH SAID PATHS FOR SUPERHEATING THEREOF, (E) ADDITION MEANS COMMUNICATING WITH EACH OF SAID CONDUIT MEANS, EXCEPT THE ONE CONNECTED TO THE LAST PATH, TO ADD WATER TO SAID CONDUIT MEANS INTERMEDIATE OF EACH SUCCESSIVE PATH TO DESUPERHEAT SAID SUPERHEATED STEAM AND TO INCREASE THE QUANTITY THEREOF, (F) REMOVAL MEANS CONNECTED TO SAID LAST PATH FOR REMOVING SUPERHEATED STEAM FROM SAID VESSEL. 